fix failing test. Result is always string

Change-Id: Ifbc9b2f768fd616e2bb52fff184ba67078d525bc
Reviewed-on: http://review.couchbase.org/37995
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>